Electrographic display apparatus and method.



M. R. HUTCHISON.

ELEOTROGBAPHIG DISPLAY APPARATUS AND METHOD.

APPLIQATION IILED 0017.30, 1905 1,068,774. Patented July 29, 1913.

2 SHEETS8HEET 1.

M. R. HUTCHISON. ELEGTROGRAPHIG DISPLAY APPARATUS AND METHOD.

APPLICATION FILED OQT.30, 1905. 1,068,774. Patented July 29, 1913.

2 SHEETSSHEET 2.

E R -U A: a 1 :A M fi i A. X

$51 1 whom lu g 0 l PLANOGRAFH COHWASHINQTON, D. CA

or material be capable of electro-chemical re- MILLER REESE HUTCHISON,

0F BBONXVILLE, NEW YORK.

ELECTROGB APHIC DISPLAY APPARATUS AND METHOD.

Application filed October 30, 1905.

To all whom it may concern:

Be it known that I, MILLER REESE HUTCH- rsox, citizen of the UnitedStates, and resident of Bronxville, in the county of WVestchester andState of New York, ha e invented certain new and useful ElectrographicDisplay Apparatus and Method, of which the following is a specification.

The inventions herein disclosed relate to the production of visibleindications or designs as by writings, sketches, etc., the markingsthereof being preferably in marked contrast to the background.

My method depends upon mechanical, chemical or electrolytic change,produced by the passage of an electric current through, over or upon amaterial capable of visible change of state, or of color, in response tothe electric current. The material to be thus visibly changed as to itsstate or color, may be any that is suitable or desirable, but I preferone depending for its operation, on electro-chemical, or electrolyticreaction or decomposition, preferably one which causes the mark orindication by a change of color of the electrolytic material, andpreferably one which operates by cathode reaction to i produce aprecipitate or solution, preferably of striking color. It is highlydesirable,- though not necessary, that such electrolyte versal, bychange of polarity, to cause disappearance of such colored precipitateor solution, thereby effecting erasure of the marks. If desired, ananode reaction may be utilized to produce the' mark and a cathodereaction to erase it.

he apparatus consists essentially of a surface of such character as willbe capable of the changes above described, together with means forbringing the electric current into operative relation thereto. I mayutilize the surface of an absorbent body, such as blotting paper, feltor unglazed pottery, moistened with the electrolyte, though it is quitewithin the spirit of my invention to utilize the liquid surface of abath of a suit able electrolyte. Quite pleasing effects may be producedin this way, though if the electrolyte is very fluid, they may besomewhat l Specification of Letters Patent.

"liquid. Solidifiedor semi solid which the porous material rests, porousconducting surface,

lccting, because of the tendency of the coloring matter to be displacedand the design confused, either by diffusion or by convec- Patented July29, 1913.

Serial No. 285,141.

tion currents. The latter difficulty may be minimized by using a thinlayer or film of the liquid upon a smooth surface. Very pleasing effectsmay be produced by using a sheetof metal with its surface freshlycovered over or wetted with a film of fluid electrolyte. In such case,the surface and the film should be of such character as to maintain thecontinuity of the film without tendency to agglomeration in drops. Abody of viscous electrolyte may be employed or a fluid electrolyte maybe rendered more or less viscous in any desired way, as by glycerin orgelatin solutions. De-

signs, etc., may be sketched in three dimensions or in a singleplaneinthe body of the gelatin or jelly-like sheets may be employed.

When porous material is employed as a supporting mediumfor the sensitivesubstance, the moistening may be effected by hand or by a fountain pador reservoir upon or said material may form a horizontal or verticalWallof the reservoir. Many-other variations will suggest themselves.-

FOI' many reasons, I prefer to use plain paper impregnated with asuitable material, adapted to form an electro-chemically, sensitiveelectrolyte, upon the application of moisture. I employ any suitablesupport for the paper, preferably one formed with a and in connectiontherewith, any suitable means for causing the current to pass tothe'front or visible side of the paper from said conducting surface orvice versa. I have contemplated forming a composite sheet comprising oneor more sheets of impregnated paper with one or more sheets of tin foil.

The essentials of my electro-graphic apparatus may be embodied in avariety of forms, for a variety of purposes. Among the appliancescontemplated, are display boards for advertisements, bulletins,-etc.,and magic easels for the performance of various magical tricks, eitherin business places, shop windows, etc., or for parlor entertainment, orfor semi-dramatic theatrical performances.

Having thus explained the nature and objects of my invention, I willproceed to describe the same more particularly in conused in place ofthat shown in Fig. 2, es-- pecially where the device is intended formystification of the spectator. Fig. 5 is a vertical transverse sectionof the device shown in Fig. 4. Fig. 6 is a detail of the marking rollerof Fig. 2, at right angles to the position shown in the latter figure.Fig. 7 is a detail of a modified form of writing surface. Fig. 8 is asectional view of a toy. Fig. 9 is a sectional detail of a reservoir.Figs. 10 and 11 are views of a modification.

While I show and describe with some accuracy and in some detail, variousspecified forms of the device, it will nevertheless be understood thatthe invention is as broad as above indicated, and I do not limit myselfto any specific embodiment thereof I Referring to Fig. 1,1 is a suitablesupport which may conveniently be ofthe character and size. of a smallblackboard, signboard or picture, though of course, there is no neces-;sary limitation as to size. Upon -or in the front surface thereof, isformed. or mounted a conducting coating or surface',--2=, which in turnis covered and concealed by the sen-" sitive paper or other writingsurface, 3. Any porous material may be used for-this purpose, and it maybe made a permanent part ofthe structure, or as in the case-of paper,may be held by removable thumb tacks or other fastening 4, for readyadjust ment and renewal at desired intervals.

- Suitable circuit connections for the marking surface 2 and the marker,5, are provided and in the apparatus shown in Fig. 1, they areintentionally arranged in the most open and visible manner, with thepurpose that when the device is used in a show window or similar place,for advertising, even the most ignorant spectator will appreciate thefact that the writing or artistic composition being traced by anoperator is electrically produced. To this end, wires 6, 7 connected toany suitable direct current source, are led to the contacts 8, 9 andcross connected to oppositely located similar contacts, 10, 11.Intermediate the two opposite pairs of contacts, is the double throwswitch 12, comprising separate blades 13, 14 connected respectivelythrough 1:") and 16, to the marker 5 and to the conducting surface orsheet 2.

The marker is preferably of the construction shown in Fig. 2, althoughit may be of any other convenient construction, as for instance, thatshown in Figs. 4 and The form in Fig. 2 comprises a conducting shank,17, provided with an insulated covering, 18, to be grasped by theoperator. At one end, the shank 17 is provided with a Suitable head, 19,upon which is mounted a roller marker, which as will be evident from thedrawing, is mounted similarly to a swiveled roller bearing caster, theswivel comprising the integral head 2-0, smooth shank 21, and reducedscrew 23, the same having a square shoulderadapted to be screwed homeagainst the face of enlargement 19, to lock the swivel pivot againstaccidental unscrewing. Suitable anti-friction balls and annular groovesare provided between the face of said enlargement and the backside ofthe stirrup or bifurcated arm, 25. In the bifurcation of the latter andmounted upon axle 26 are the-spaced disks'27, constituting in effect aroller 1 adapted .to have anti-friction bearing on the'marlcing-surface.Thisis desirable where'thesurface'used is moistened blotting paper whichmight be worn or roughened by frictional or sliding marking dvices- Thedisks 27--are spaced apart eitherby washers or by thickening of thehubs-thereof, the lat-ter'method being shown inthe drawing.- The outerdisks are preferably beveled off on their outer sides or the arms-'25bowedoutwardly to give a pro-per. clearance to. the outer sides of thedisk, as there is-sometiines a tendency to accumulation of :wetiblottingpaper and chemical products ofwelectrolysis eitherfrom the metal of themarker which serves as an electrodeor from the electrolyte. The disks 27rotate independently because in tracing curves and angles, the disks onthe outer side of the curve must travel farther and therefore rotatefaster than those traveling the shorter'path on the inner side of thecurve; In default of such provision, there would necessarily be the slipand rubbing contact which it is desirable to avoid. The circuitconnection to the marker may be at any convenient point, as at thebinding screw 28. At the rear end of the handle 18, and conductivelyconnected with the core 17, is aroller 19, preferably secured by screw30.

The operation of the above apparatus is as follows: The marking surfaceis charged with a solution such as phenol phthalein, or if alreadyimpregnated with such substance, moistening only will be necessary. Theswitch is then thrown up to make contact with terminals 8 and 9, so thatthe current will flow through 6, 8, l t and 16 into 2, and then into 3,whence it will emerge through roller 27 back through 15 and 9 andthrough lamp 31 and conductor 7, cut to line.

With the solution described, the disks 27 will, in this situation, becathodes of an 139 electrolytic conducting material included in acircuit, and when phenol phthalein is the solution employed there willbe deposited at such cathode a very vivid and very beautiful red orcrimson precipitate, forming a most striking contrast with the white orneutral back ground presented by that part of the surface which has notbeen colored by the passage of the current therethrough. The colorappears instantaneously at the touch of the roller, and it is thereforepossible for an artist, penman or advertiser to write or draw anydesired design, picture or writing or printed legend descriptive ofgoods or to do each alternately, for the amusement and instruction of acrowd. When the device is used for quasi-scientific instruction of themasses, as an incident to the main object of advertising, all theconnections are preferably in full view, as is also the incandescentlamp, 31. Every time the roller 27 touches the paper, the circuit isclosed and the light 31 flashes up, continuing to glow as long as theroller continues in contact with the electrolytic conducting surface, 3.

The operator may at any time reverse the double throw switch 12, and usethe smooth roller which is preferably of greater width than roller 27,for the purpose of partly or wholly erasing the red designs or writingmade while the switch was in the first position. This is because phenolphthalein is almost completely reversible electro-chemically, andwhenever the current is caused to pass in the reverse direction, the redprecipitate returns to its original colorless condition. It is desirablethat the porous body be thick enough to prevent any red precipitateforming at points of contact of the back side of the paper withconducting plate 2, from diffusing and spreading out through the paper,so as to be visible on the front side thereof. This may occur when thecurrent is reversed and 2 becomes the cathode.

One reason for making the marking surface in the form of separated disks27 is because the desired cathode reaction is so pronounced anddiffused, particularly on the moist paper, that the spread of thecurrent and the diffusion of the precipitate will completely fill in fora considerable distance on each side of the points of contact. Of courseit is possible to make the separation of the disks 27 sufiicient so thatthere will remain white streaks between the red, so that the marksinstead of being broad, solid lines will consist of parallel lines ofwhite and red.

Nhenever phenol phthalein, or any similar electrolytic solution, capableof practically complete electro chemical reversal is employed, adifferent method of procedure may be adopted. For instance, proceedingas before to put in position and prepare a fresh moistened sheet, 3, theoperator may throw the switch into the uppermost position and using theroller 29, may pass it over the entire surface of the sheet, changingthe surface thereof to a uniform solid red. Then reversing the switchand using either 27 or 29 as the marker, he may produce white lines onthe red background, because in this relation of parts, the marker beingthe anode, produces the hereinbefore described chemical reversal wherebythe red precipitate is restored to the colorless condition.

It will be understood that many other sensitive electrolytes besidesphenol phthalein may be used, and these will readily suggest themselvesto one familiar with the art. Among those possible of use are solutionssuch as sympathetic inks of the cobalt compounds. These give a blue markinstead of a red, and it is possible to prepare a paper impregnated inone part with one solution and in another with another solution, or tohave opposite surfaces impregnated with different solutions, with anintermediate sheet of tin foil arranged after the manner shown in Fig.7.

A striking effect may be produced by impregnating. a one or moredifferent color producing electrolytes in the paper in the formof apredetermined advertising pattern, so that the electrically producedmark-.

ings will appear in different colors on different parts of the surface,and when the entire sheet is traced over with amusing or instructivematter, the pattern of the advertising matter will be revealed. To bestproduce this effect, the impregnated, primarily invisible pattern shouldbe on broad lines and on a large scale, while the writing or designtraced by the operator should be on a comparatively small scale. Theadvertising matter may constitute the impregnated pattern or theoperators design or both, or one or both designs may be artistic orinstructive.

When my invention is to be applied for purposes of mystification, as inparlor magic or theatrical performances, the entire mechanism of theoperation should be concealed so that the operation will appear asmysterious as possible, and for such purposes I have indicated in Fig.3, certain arrangements which are capable of being varied indefinitelyto suit the conditions, or the taste of the user. In this figure, lindicates the support, 2 is the conducting electrode surface, .2 is apad of any suitable absorbent material adapted to serve as a res ervoirof electrolyte, to maintain the removable sheet 3 in moistenedcondition. In this case, the Wires 6, 7 and lamp 31, together withcontacts 8, 9 10, 11 and reversing switch 12 and marker connection 15are preferably concealed. The contact plate 41 is located out of sightof the audience, and is adapted to form an electrical connection throughthe heel of the'operator with the conductor 42, any of the expedientscommonly employed in the art being available for efiecting thisconnection. The reversing switch 12 is preferably flush with the floorand may be coveredby a rug, or concealed in any other desired way. It ispreferably normally spring pressed by spring 43 in such direction thatthe marker is a cathode and gives the red indication when phenolphthalein is the electrolyte. The connection 16' corresponding to 16 isconcealed in the legs of an easel upon which is supported the magicboard or picture 1, 3. In this connection, durability of the sensitivesurface is a minor consideration and I prefer to form the marker with asmooth contact surface 27 subordinating the desirable anti-frictionbearing to the. purpose of concealment of the contact. The latter isclearly shown in -.Figs.-4 and 51:0 consist of a removable finger tipcomprising a conducting outer surface, conveniently of sheet metal,lined with non-conductingmaterial' such as rubber, as indicated atz44.It is shaped to conform to the finger tip and to be as inconspicuous aspossible. In the form shown, it is adapted to beheld to -'-thefin-' gerby bands'45, 46, which may be simple elastic, preferably white-in color,or which may be of metal, as shown, and preferably white. With thisarrangement, the operator may make connectionthrough one leg with thecontact41, and write -anydesired' pattern upon the surface 3.By:inco1ispicu-" ous and unnoticed movement ofrthe other foot, he mayopen the switch,:thereby losing his magic power to produce the marks onthe board, or he may press still harder and reverse the current, therebycausing the contact 27 to become an anode, so that it will no longerproduce magic designs and will cause those already produced todisappear. Obviously, there may be two performers, each provided withhis own contact 41 and reversing switch 12 and the reversing switch ofeither may be controlled by the other. One may write and the other mayerase. The permutations and combinations of such devices and expedientsand the dramatic possibilities thereof will be obvious to those skilledin such matters.

In Fig. 9, 61 is a tank or reservoir containing a desired electrolyticsolution 62, in contact with a porous plate 63, preferably of unglazedpottery. In this device, the entire rear surface of the sensitive plateis in direct contact with a comparatively large supply of electrolyte.The conducting surface 61, which is normally the anode, is distant fromthe visible sensitive surface 63, so that when the current is reversedto erase the colored markings on 63, said surface 63 is completely outof range of possible diffusion of any coloring matter which may beprecipitated on 61 acting as an anode. This is also one of theadvantages of a thick pad 2, as shown in Fig. 3. The reservoir 61 may befilled and emptied through the screw closed opening 64.

In all the forms, the electrodes should be of material such as will notseriously interfere with the electro-chemical reaction, as for instance,aluminum for the normal anode 2 and phosphor-bronze for the cathods 5.The material of the electrodes may however be copper or cobalt compoundsas may serve to facilitate and even participate in the desired reaction,either to produce marks or to erase them. Any cobalt salts, such as areused for sympathetic ink, which is to be invisible whenv written and tobecome blue on exposure tocheat, may be used for this purpose.

=The broad-method of this :invention may be applied to any desiredarrangement of fixed or movable electrodes operated' mechanically orelectrically according to a predetermined pattern or at will. For in-.stance', any of the. display apparatus utilizing incandescent lamps toform elements: of

a pattern, designforlegendmay be utilized by. substitutingflafcathode.reaction as the display elementin place of the incandescent lamp. *Toend; cathodes immersed in. or:..moistened -witti a solution ofelectrolyte may be used iii-connection with pattern operatedcommutator-S or switchesto cause ourfirent to pass into'oriout of one orany desired number of such cathodes from one or more anodes, which. mayor may not be concealed-:- 1; g

Anodes and cathodes may be given any desired configuration-and may begrouped in any desired way. I have diagrammatically'indic'ated' in Figs.10 and If illustrative forms of such arrangement. In Fig. 10 groups ofelectrodes having the'configuration of letters are arranged foroperation in connection with electrolyte applied in any desired way,: asby immersing said electrodes in a. bath-having a transparent wall. Insaid Fig. 10 thetank or other support 71 is shown in vertical section.The electrodes are given suchconfiguration as to represent a: desiredlegend or design, as for instance, Bone soap and It cleans. One of thenumerous possible methods of connection shown in said Fig. 10, whereinthe electrodes representing the legend Bone soap are conductivelyconnected in parallel with each other, and preferably also withelectrodes 7 2, 7 3 adjacent to the electrodes It cleans, which latterare of opposite polarity and are connected in parallel with theelectrodes 7 4, 75, adjacent to the electrodes constituting the legendBone soap. When arranged '76, operating to as described, the surface of72 should preferably be substantially equal to the surface It, and thesurfaces 73, 74, and 75 re spectively, substantially equal to the totalsurfaces of Cleans, Bone, Soap. As will be obvious, these electrodes 72,73, 74 and 7 5 are hardly necessary in a solution because of the law ofresistances and distribution of current above referred to, whereby thereis a tendency to equalization of current density over all parallelconnected electrode surfaces.

The two legends are connected to a commutator 76, adapted toperiodically reverse the polarity of the battery or other source ofdirectcurrent indicated at 77. Thus arranged, and with the rotation ofthe commutator properly timed, the colored precipitate will appear,changing the legend Bone soap from the normal color of the metal orother conducting material to the red or blue or other color. Uponreversal of the current, the legend. It cleans will similarly becomecolored, while the color will gradu-. ally disappear from the legendBone soap]? Where thin moistened paper is used,.the sup plementalelectrode surfaces 72, 73, 7.4;and 75 are more essential to reasonablylow-re sistance and practically uniform distribution of density ofcurrent flow, because in, the

case of thin paper, the spreading oflines of flow between electrodes ispractically limited to the two dimensions of a plane and is there-r foreless marked than in the case of the three dimensions of a body ofelectrolyte.

In Fig. 11, I have shown a modification wherein the two legends arearranged asthe electrodes of two different solutions, one giving acrimson color andthe other a blue color as the characteristic electrodereaction. These colors are particularly appropriate for use respectivelywith, the namestHar vard and Yale)? I As will be obvious to thoseskilled m n art of electric advertising, the use of time cut outs, afterthe manner of the commutator cut in and cut outiportions of a pattern orlegend, is capable of wide variation both as to the time and as to the.portions of the pattern which will becut out.

In all arrangements the resistances will of course be adjusted inaccordance withthe character of thesource of supply of current and thenature of the work to be done. In the form shown in Figs. 1 and 2, theserially arranged incandescent lamps 31 serve ascurrent limitingdevices. One or more of these may be used either in series or parallelto suit the conditions; or any suitable form of rheostat may be used asa supplement to or substitute for the same.

Any of the marking electrodes used to trace patterns, designs orwritings may be used in connection with crayons, pencil, pens or otherconventional or usual graphic inconnection ,throu'gh. th

greater current to erase a mar struments, anywhere where marking isdesirable for display, instruction or amusement; and the writing surfacemay be supplied with printed designs to be traced over and colored orotherwise illuminated by the electrical current ,reaction.

In Fig. 8 I have-shown a device adapted forjuvenile use as a toy oreducational appliance. The device a slate comprising a plane surface 81,surrounded by a frame 82. 81 may be conducting or supplied with aconducting surface adapted to receive a sheet of sensitive paper 83/ Asuitably insulated pencil 84: having a conducting tip 85, adapted toserve as a marking electrode, may be serially connected with a suitablesource of current, the other pole of which is connected to the support81. The source may be a case 86, containing three or four dry cellsconnected to a suitable resistance with the circuit just described. I

A plain sensitive sheet or a composite sheet consisting of paper, withtin foil either as a backing .toa single sheet, orinterleaved betweentwo sheets, may be prepared in a continuous sheetand mounted uponrollers as indicated. in :Fig. 7.- The arrangement may be as shown, tounwind from a supply roller andrewind. on a storage roller;

or one roller only'ma'y be used, a continuous sheet being provided withsuitable perfora tions for ready separation of a convenient length..Wherrthe tin foil, or otherconductor, :2 is interleaved between twosheets, 3, as connection of one side of the circuit may be madewith 2,.in any, desired way, as by be as s. u to secure the sheet afterthemanner shown in Fig. 1 where the-tin foil .or other conducting sheet' isused. .merely as a backing for a. single papepsheet, 3,..9. contact maybe Y made. with 2, directly, through any suitable terminal, at. the backside of the same, as for .instance,..a, terminal. set in' the support1,. Fig. 11. desired, the rollers may be operated automatically atvintervals, and the continuous web may be .a.single thin sheet ofpapenmoistned with a suitable electrolyticsolution. The latter.arrangenient is well adapted for use where the marking or indicatingelectrode is on the backsideof the paper and the colored design isintended to show through on the front side.

With some electrolytes, it will be found that it requires either a loner time or a e. render a precipitate colorless) than it does to causesuch precipitate in the first instance. For this reason, it willsometimes be found desirable to arrange the double throw switches ofFigs. 1, 2, 8 and 9, or the commutating apparatus of Figs. 10 and 11 insuch manhas a general form of .100 indicated n said Fig. 7, conducting Yner that when the direction of Current is changed for the purpose ofrendering the precipitate Colorless, a desired amount of increase ofcurrent shall be rendered available, either by cutting out resistance orby increase in applied electro-motive force, as will be evident fromFig. 1, wherein both of these expedients are utilized. To do this, it isonly necessary to put a resistance in the lead 6 to the contact 8 of thedouble throw switch, and a battery or other additional source of directelectromotive force in the connection to the contact 11.

Many modifications and combinations of the above described elements,features and methods will readily suggest themselves as within thesphere of my invention.

I claim:

1. A display device comprising a body having a display surface and anelectric marker comprising an antifriction roller mounted upon a handlefor universal movement and movable into and out of contact with saidsurface, in combination with a source of electromotive force andconnections whereby circuit is closed through said marker and saidsurface whenever they are brought into contact.

2. An electrically conducting display surface comprising a body havingadisplay surface and an electric marker comprising an antifriction rollermountedlupon a handle for universal movement and movable into and out ofcontact. with said surface, in

combination with a source of electromotive force and connections wherebycircuit is closed through said marker and said surface whenever they arebrought into con tact. a.

3. A graphic device comprising an electrolytically conducting body,adapted to produce visible effects in the electrolyte,

upon passa e of electric current in one direction, an to cause sucheffects to dlsap pear, when the current is reversed, in combination witha source of direct current and means for causing said current to' passthrough said body in either direction at will.

4. A graphic device comprising an electrolytically conducting body,adapted to produce visible effects at a cathode, and to cause suchetfects'to disappear,"when the current is reversed, in combination witha source of direct current and means for causing said current to passthrough said body in either direction at will.

5. A raphic device comprisin an electrolyticzilly conducting body, aapted to produce color effects at one electrode, upon passage of currentin one direction, and to cause such color effects to disappear, when thecurrent is reversed, in combination with a source of direct current andmeans for causing said current to pass through said body in eitherdirection at will.

6. A raphic device com rising an electrolyticailly conducting be y, incombination with a direct current source and means for causing electriccurrent to flow out of a surface of said body, said means comprising aconcealed anode of large area and a visible cathode of small area.

7. A graphic device comprising an electrolytically conducting bodyadapted to pro duce color effectat regions where electric current flowsout of said body, in combination with means for causing such flow in theregion of a visible portion of the surface of said body, said conductingbody bein sufficiently thick so that color effects produced on one sidethereof are not visible upon the other side.

8. A graphic device comprising an electrolytically conducting bodyadapted to pro duce a visible effect at one electrode, upon passage ofcurrent in one'direction, in combination with a conductor adapted for application to the surface of said body, as a cathode of the electrolyteand means for reversing the direction of current flow through saidconductor.

9. A graphic device comprising an elec trolytically conducting body,adapted to produce color effects at an electrode, upon passage ofcurrent in one direction, in combination with a conductor adapted forapplication to the surface of said body, as a cathode of the electrolyteand means for re-' versing the direction of current flow through saidconducton' I 1O. A. graphic device comprising an elec trolyticallyconducting body, in combination'with an anode of considerable area,extending over the rear surface thereof, and a coiiperating movablecathode of relatively small area on the front side thereof, togetherwith means for reversing the polarity of said anode and cathoderespectively.

11. A graphic device comprising an electrolytically conducting body, incombination with an elect-rode surface of considerable area, and asecond electrode of relatively small area, said electrolyticallyconducting body being adapted to produce a colored substance adjacentone electrode only, the thickness of said conducting body beingsufficiently great so that color effects produced by an electrode on onesurface of the body will not be visible on the other surface.

12. A graphic device comprising an elec trolytically conducting body, incombination with an electrode surface of considerble area, and a secondelectrode of rela tively small area, said electrolytically conductingbody being adapted to produce, under electric current flow, a coloredsubstance adjacent one electrode only, together with means for reversingthe direction of current flow through such electrode.

13. A display device for advertising, amusement, etc., comprising a bodyof suitable material having an electro-chemically sensitive surface, incombination with electrical means for causing the material at or nearsaid surface, to produce a colored substance, together with meanscontrollable at will for causing said substance to become invisible.

14;. An antifriction marking contact device capable of movement in alldirections against a display surface and comprising laterally adjacentrolling contact surfaces mounted for independent rolling contact atdifferent rates.

15. An anti-friction contact device for marking purposes capable ofmovement in all directions against a display surface and comprisinglaterally adjacent independently rotatable disks.

16. An anti-friction contact device, for marking purposes capable ofmovement in all directions against a dis lay surface and comprisinglaterally space adjacent, independently rotating disks.

17. A graphic device comprising a body having a marking surface, and ananti-friction marker comprising a shank and a roller bearing contactsurface together with a swivel connection for said parts, the axis ofsaid swivel being out of line with the center of rotation of said rollercontact device and perpendicular to a plane containing said centers ofrotation and a perpendicular from the latter to said axis and electricalconnections from a source of electricity to said body and said marker.

18. A graphic device comprising a body having a marking surface and amarker comprising a shank and sectional, spaced roller contacts and aswivel device securing the latter eccentrically to the axis of theformer and electrical connections from a source of electricity to saidmarking body and marker.

19. As an article of manufacture, a porous sheet impregnated withdifferent electrolytic materials in different portions thereof, saidelectrolytic material being adapted to produce different colors underinfluence of the electric current.

20. As an article of manufacture, a porous sheet impregnated withdifferent electrolytic materials in different parts thereof according toa predetermined design, pattern or legend, said electrolytic materialbeing adapted to produce different colors under influence of theelectric current.

9.1. In a graphic device, a body containing an electrolyte subject tochange of appearance when an electric current is passed through thesame, an electric cont-act device movable freely on and over the surfaceof said body while maintaining contact therewith so that unbroken linesand delineations may be produced by electro-chemical action at thetraveling point of contact, a source of direct current, a connectionfrom one pole of said source to said body of electrolyte, and aconnection from the other pole of said source to said traveling contactdevice.

22. In a graphic device, a body containing an electrolyte subject tochange of appearance when an electric current is passed through thesame, an electric contact device movable freely on and over the surfaceof said body while maintaining contact therewith so that unbroken linesand delineations may be produced by electrochemical action at thetraveling point of contact, a source of direct current, a connectionfrom one pole of said source to said body of electrolyte, and aconnection from the other pole of said source to said traveling contactdevice, said electrolyte being of a nature such that the lines ordelineations produced as aforesaid become invisible when the current isreversed, and means for reversing the direction of the current.

23. In a graphic device, a body containing an electrolyte subject tochange of appearance when an electrlc current 15 passed through thesame, an electric contact device movable freely on and over the surfaceof said body while maintaining contact therewith so that unbroken linesand delineations may be produced by electrochemical action at thetraveling point of contact, a source of direct current, a connectionfrom one pole of said source to said body of electrolyte, and aconnection from the other pole of said source to said traveling contactdevice, said body of electrolyte being such that the color effects ofthe delineations and the back ground thereof on the body containing thesame are reversible by reversal of the current, and means for reversingthe current.

24. In a graphic device, a body containing an electrolyte subject tochange of appearance when an electric current is passed through thesame, an electric hand controlled contact device movable freely on andover the surface of said body while maintaining contact therewith sothat unbroken lines and delineations may be produced by electrochemicalaction at the traveling point of contact, a source of direct current, aconnection from one pole of said source to said body of electrolyte, anda connection from the other pole of said source to said travelingcont-act device.

25. In a graphic device, a body containing an electrolyte subject tochange of ap pearance when an electric current is passed through thesame, a substantially frictionless electric contact device movablefreely on and over the surface of said body while maintaining contacttherewith so that unbroken lines and delineations may be pro- Signed atNew York city in the county of duced by electrochemical action at thetrav- New York and State of New York.

cling pointof contact, a source of directcurrent, a connection from onepole of said MILLER REESE HUTCHISON' source to said body of electrolyteand a con- Witnesses: nection from the other pole of said source to G.C. DEAN, said traveling contact device. A. G. STAGE.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents.

- Washington, D. C."

